Species-specific suppression of histone H1 and H2B production in human/mouse hybrids.

Ten human/mouse hybrid cell lines that segregate either human or mouse chromosomes were examined for the expression of human- and mouse-specific histones H1 and H2B. Results of this study indicate that the human and mouse chromosomes in hybrid cells that segregate human chromosomes (M greater than H hybrids) contain only mouse histone H1 and H2B. Chromosomes in hybrid cells that segregate mouse chromosomes (H greater than M hybrids) contain only human H1 and H2B histones. Loss of the ability to produce either human or mouse histones does not seem to be due to the loss of specific human or mouse chromosomes because M greater than H hybrids retaining at least one copy of each human chromosome contain only mouse H1 and H2B and H greater than M hybrids retaining at least one copy of each mouse chromosome contain only human H1 and H2B histones. These results, together with those concerning histone H4 acetylation levels and ratios of variants of histones H3 and H2A that are like those in the dominant parent cell type, indicate that the control mechanisms affecting H1 and H2B expression in H greater than M and in M greater than H hybrid cells affect expression of histones H2A, H3, and H4 genes as well. The present data thus support the hypothesis that none of the histone genes that are active in the recessive parent cell type is expressed in hybrid lines that segregate recessive cell chromosomes.     

Histone H2A subtypes associate interchangeably in vivo with histone H2B subtypes.

The yeast Saccharomyces cerevisiae contains two primary sequence subtypes of histone H2B (H2B1 and H2B2) and of H2A (H2A1 and H2A2). Mutants in each of the H2B subtypes have been used to show previously that yeast cells lacking one or the other, but not both, of the H2B proteins are viable. Because H2A protein interacts in the nucleosome with H2B, we wished to determine whether specific H2A subtypes must interact with specific H2B subtypes. We describe experiments in which frameshift mutations were introduced into both of the H2A genes in vitro and the mutant genes integrated into the yeast genome, replacing the wild-type H2A genes by a subsequent recombination. Using these mutant (hta1- and hta2-) strains we find that neither H2A gene has a unique essential function during any phase of the yeast life cycle, although strains homozygous for hta1- grow more slowly. However, one functional H2A gene is required for viability because cells mutant in both H2A genes arrest at spore germination prior to bud separation. By combining these H2A mutations with the H2B mutations obtained previously, we show that all combinations of H2A and H2B subtypes produce viable cells. From these genetic experiments and electrophoretic analysis of the histone proteins of these mutants we conclude that the H2A subtypes can associate interchangeably with the H2B subtypes.     

Relationship between arsenic exposure and histone ubiquitination modifications of H2A and H2B in human peripheral blood leukocytes

正Objective To detect the modification levels of H2AK119 ubiquitination(H2AK119ub)and H2BK120ub,and to analyze the relationship between the levels of H2AK119ub,H2BK120ub and arsenic exposure.Methods A cross-sectional study was conducted in typical areas of drinking water type of endemic arsenicosis in     

C2株蓝氏贾第鞭毛虫组蛋白H2B基因的克隆与同源性分析

目的 获取C2株蓝氏贾第鞭毛虫H2B组蛋白基因序列,与WB株蓝氏贾第鞭毛虫及其他物种进行同源分析。方法 PCR扩增获取H2B组蛋白基因,连接pGM-T载体,转化E. coli DH5α感受态宿主细胞,挑选阳性克隆并进行序列分析,与美国WB株蓝氏贾第鞭毛虫及模式生物H2B组蛋白基因和蛋白序列进行同源分析。结果 测序C2株蓝氏贾第鞭毛虫H2B组蛋白基因序列,同源比对结果显示其基因序列与美国WB株完全一致,进化树分析表明贾第虫H2B组蛋白基因在进化过程中与其他物种分化较早。结论 蓝氏贾第鞭毛虫H2B组蛋白基因同源分析结果显示贾第虫与其他现存真核生物亲缘关系较为疏远,为进一步研究蓝氏贾第鞭毛虫的生物进化地位提供有价值的资料。     

Structure and function correlation in histone H2A peptide-mediated gene transfer

Histone H2A has been found to be efficient in DNA delivery into a number of cell lines. We have reasoned that this DNA-delivery activity is mediated by two mechanisms: (i) electrostatically driven DNA binding and condensation by histone and (ii) nuclear import of these histone H2A.DNA polyplexes via nuclear localization signals in the protein. We have identified a 37-aa N-terminal peptide of histone H2A that is active in in vitro gene transfer. This peptide can function as a nuclear localization signal and can bind DNA. Amino acid substitutions that replace positively charged residues and/or DNA-binding residues of this peptide obliterate transfection activity. The introduction of a proline in the first turn of an alpha-helix of this 37-mer obliterates transfection activity, suggesting that the integrity of the alpha-helical structure of the N-terminal region of histone H2A is related to its transfection activity.     

Evidence for both histamine H1 and H2 receptors on human articular chondrocytes.

Using specific histamine H1 and H2 receptor antagonists, evidence is presented for the existence of both H1 and H2 receptors on human articular chondrocytes in vitro. Stimulation of the H1 receptor by histamine (range 0.18 to 17.8 mumol/l) significantly increased prostaglandin E (PGE) production, while activation of the histamine H2 receptor increased intracellular cyclic adenosine-5'-monophosphate (AMP). The histamine H1 antagonists mepyramine and tripelennamine blocked the histamine induced increase in PGE production, and the H2 antagonists cimetidine and ranitidine prevented the increase in intracellular cyclic AMP. These observations suggest that mast cell-chondrocyte interactions mediated via histamine may contribute to some of the pathophysiological changes observed in joint disease.     

Decreased histone H2B monoubiquitination in malignant gastric carcinoma

AIM:To investigate H2B monoubiquitination(uH2B)and H3K4 di-and tri-methylation(H3K4-2me,H3K4-3me)levels and their clinical significance in gastric cancer(GC).METHODS:Immunohistochemistry(IGC)was used to detect the differential levels of uH2B,H3K4-2me and H3K4-3me modifications in GC specimens from chemo/radiotherapy-na ve patients who underwent potentially curative surgical resection(n=159)and in a random sampling of non-tumor gastric epithelium specimens(normal controls,n=20).The immunohistochemistry(IHC)-detected modifications were classified as negative,low-level,or high-level using a dual-rated(staining intensity and percentage of positively-stained cells)semi-quantitative method.The relationships between uH2B modification levels and clinicopathological parameters of GC were assessed by a Wilcoxon rank sum test(pairwise comparisons)and the Kruskal-Wallis H test(multiple comparisons).The correlation between uH2B modification and survival was estimated by Kaplan-Meier analysis,and the role of uH2B as an independent prognostic factor for survival was assessed by multivariate Cox regression analysis.RESULTS:The presence and level of H3K4-2me and H3K4-3me IHC staining was similar between the normal controls and GC specimens.In contrast,the level of uH2B was significantly lower in the malignant gastric tissues(vs normal control tissues)and decreased along with increases in dedifferentiation(well differentiated>moderately differentiated>poorly differentiated).The level of uH2B correlated with tumor differentiation(P<0.001),Lauren’s diffuse-and intestinal-type classification(P<0.001),lymph node metastasis(P=0.049)and tumor-node-metastasis stage(P=0.005).Patients with uH2B+staining had higher 5-year survival rates than patients with uH2B-staining(52.692±2.452 vs23.739±5.207,P<0.001).The uH2B level was an independent prognostic factor for cancer-specific survival(95%CI:0.237-0.677,P=0.001).CONCLUSION:uH2B displays differential IHC staining patterns corresponding to progressive stages of GC.uH2B may     

Reassessment of histone gene expression during cell cycle in human cells by using homologous H4 histone cDNA.

The representation of H4 histone mRNA sequences in RNAs isolated from G1 and S phase HeLa cells was assessed by use of a homologous H4 histone cDNA. S phase cells were obtained by double thymidine block, and G1 cells were obtained by double thymidine block or mitotic selective detachment. Nuclear and cytoplasmic RNAs from S phase cells hybridized with H4 histone cDNA as did nuclear and cytoplasmic RNAs from G1 cells synchronized by double thymidine block. In contrast, significant levels of hybridization were not observed between H4 histone cDNA and nuclear, polysomal, or postpolysomal cytoplasmic RNAs of G1 cells synchronized by mitotic selective detachment. Double thymidine block yields a G1 cell population containing 20-25% S phase cells whereas the G1 population obtained by mitotic detachment contains less than 0.1% S phase cells. The ability of H4 histone cDNA to hybridize with the RNAs from G1 cells obtained after release from double thymidine block can therefore be explained by the presence of S phase cells in such a G1 population--an artifact of the synchronization procedure. We interpret these results to be consistent with the presence of H4 histone mRNA sequences during the S but not G1 phase of the cell cycle in continuously dividing HeLa S3 cells.     

Structural basis of instability of the nucleosome containing a testis-specific histone variant,human H3T

A histone H3 variant, H3T, is highly expressed in the testis, suggesting that it may play an important role in the chromatin reorganization required for meiosis and/or spermatogenesis. In the present study, we found that the nucleosome containing human H3T is significantly unstable both in vitro and in vivo, as compared to the conventional nucleosome containing H3.1. The crystal structure of the H3T nucleosome revealed structural differences in the H3T regions on both ends of the central α2 helix, as compared to those of H3.1. The H3T-specific residues (Met71 and Val111) are the source of the structural differences observed between H3T and H3.1. A mutational analysis revealed that these residues are responsible for the reduced stability of the H3T-containing nucleosome. These physical and structural properties of the H3T-containing nucleosome may provide the basis of chromatin reorganization during spermatogenesis.During spermatogenesis, dramatic chromatin reorganization occurs, and most histones are eventually replaced by protamines (1). Several histone variants are highly expressed in the testis and are considered to be incorporated into the chromatin in the early stage of spermatogenesis.In humans, about 4% of the haploid genome in the sperm is reportedly retained in nucleosomes, some containing the testis-specific histone H2B, hTSH2B/TH2B (2). Interestingly, the nucleosomes retained in the sperm are significantly enriched in loci that contain developmentally important genes. In addition, histone modifications, such as acetylation and methylation, are likely to occur after the incorporation of the histone variants during spermatogenesis (1). These observations suggest that nucleosomes containing testis-specific histone variants, with or without chemical modifications, may function as epigenetic markers in the sperm chromatin.H3T is a variant of histone H3 that is robustly expressed in the human testis (3–5). We previously reported that H3T, like the conventional H3.1, can be assembled into nucleosomes with H2A, H2B, and H4 (H3T nucleosome) (6). A histone chaperone, Nap2, with 3-fold higher expression in the testis than in other somatic tissues (7), was found to be a more efficient chaperone for H3T nucleosome assembly than the ubiquitously expressed histone chaperone, Nap1 (6). Therefore, H3T may be assembled into the chromatin by a specific chaperone-mediated pathway in the testis. Comprehensive proteome analyses of nuclear extracts from HeLa cells suggested that H3T also exists in somatic cells (8, 9). However, the nucleosomes containing H3T probably comprise only a small proportion of the bulk chromatin in somatic cells, because the amount of H3T in HeLa cells is extremely low. Therefore, H3T may have a limited function in somatic cells that is currently unknown.In the present study, we found that the H3T nucleosome is significantly unstable, as compared to the conventional H3.1 nucleosome, both in vitro and in vivo. The crystal structure of the H3T nucleosome was determined at 2.7 Å resolution, revealing that, although the overall structure was similar to that of the conventional H3.1 nucleosome, structural differences were observed at both ends of the central α2 helix of H3T and H3.1. The unique physical and structural characteristics of the H3T nucleosome were attributed to the Val111 and Met71 residues that are specific to H3T.     

A yeast artificial chromosome containing the mouse homeobox cluster Hox-2.

We have isolated two genes, Hox-2.8 and Hox-2.9, from the mouse homeobox cluster Hox-2, located on chromosome 11. A 120-kilobase yeast artificial chromosome (YAC) containing a large region of the murine Hox-2 cluster, including 45 kilobases of sequence upstream of the most 5' gene, was cloned. The DNA sequence of the YAC is unrearranged relative to the genomic map. We have subcloned from the YAC insert a homeobox gene, Hox-2.8, whose homeodolmain is highly related to that of the Drosophila homeotic gene proboscopedia (pb). The expression pattern of Hox-2.8 during embryogenesis extends the trend established by genes from Hox-2.5 to -2.7 of successively anterior domains of expression in the neural tube. We have also subcloned and sequenced from a cosmid the labial (lab)-related Hox-2.9, the most 3' member of the cluster to date. These data lend further support to the idea of a common evolutionary origin of the mouse Hox and Drosophila HOM clusters. The YAC will enable us to construct modified forms of the Hox-2 cluster in yeast and to identify their effect on the phenotype of the animal in transgenic mouse strains.     

Evidence for a major cluster of lymphocyte differentiation antigens on murine chromosome 2.

The region of chromosome 2 between H-13 and H-3 has been shown to contain loci coding for a variety of other alloantigens, including Ly-4 and the locus coding for beta 2-microglobulin. Herein we show that Ly-6 and Ly-11 are coded for by genes in a segment of chromosome 2 adjacent to the H-3-H-13 region and that this segment of chromosome also contains the tightly linked loci coding for antigens Ala-1, DAG, H9/25, H-30, Ly-8, and ThB. In addition, at least one locus (and probably more) affecting susceptibility to leukemia induction is found within this gene cluster.     

A developmentally regulated chlamydial gene with apparent homology to eukaryotic histone H1.

We have developed a method for the isolation of genes whose expression is developmentally regulated from the murine strain of Chlamydia trachomatis. Here we describe the identification of two developmental stage-specific genes, one of which is predicted to encode a 26-kDa lysine- and alanine-rich protein that appears to be homologous to several eukaryotic histone H1 proteins. A substantial proportion of this homology relates to its distinctive amino acid composition. No sequence homology was observed between this protein and other bacterial "histone-like" chromosomal proteins, but homology does exist with two other recently described prokaryotic proteins. The protein is expressed late in chlamydial development, during the transition from reticulate bodies to elementary bodies. The basic nature of the protein predicts that it could bind DNA, and Southwestern blotting experiments confirm this finding. These properties are consistent with a role either in the regulation of late gene expression or in the compaction of the chlamydial genome.     

Cell cycle regulation of human histone H1 mRNA.

A cloned genomic DNA fragment containing a human histone H1 gene has been used to analyze histone H1 gene expression in two human cell lines (HeLa S3 and WI-38). The cellular abundance of histone H1 mRNA was compared with that of core (H2A, H2B, H3, and H4) histone mRNAs as a function of the cell cycle: core and H1 histone mRNA levels are related both to each other and to the apparent rate of DNA synthesis and are rapidly destabilized after DNA synthesis inhibition. The use of three synchronization protocols, and of transformed and normal diploid cells in culture, suggests that the detected core and H1 histone mRNA levels are regulated by similar mechanisms in continuously dividing human cell lines and nondividing cells stimulated to proliferate.